Control device of internal combustion engine

Abstract

An internal combustion engine is provided with a fuel injector which injects fuel into an intake port and exhaust variable valve timing mechanism which changes a valve timing of an exhaust valve. A control device executes early exhaust valve closing control which advances a closing timing of an exhaust valve when conditions for executing early exhaust valve closing control stand. The control device detects an output torque output by an engine body. At the time of deceleration of the engine, even when the condition for executing early exhaust valve closing control stands, execution of early exhaust valve closing control is prohibited when it is predicted that the output torque will become smaller than the limit torque. Thus, due to execution of the early exhaust valve closing control, a large torque fluctuation is prevented from occurring at the time of deceleration of the engine.

The invention claimed is: 
     
       1. A control device of an internal combustion engine provided with a fuel injector which injects fuel to the inside of an intake port and an exhaust variable valve timing mechanism able to change a valve timing of an exhaust valve, when conditions for executing early exhaust valve closing control stand, the control device executing early exhaust valve closing control which advances a closing timing of the exhaust valve so as to make combustion gas in a combustion chamber flow back into an intake port when an intake valve opens,
 wherein the control device is further provided with a torque detecting means for detecting an output torque which is output by an engine body and, 
 wherein at the time of a deceleration operation of the internal combustion engine, even when the condition for executing early exhaust valve closing control stands, execution of the early exhaust valve closing control is prohibited when it is predicted that the output torque which is detected by said torque detecting means will become smaller than the limit torque. 
 
     
     
       2. A control device as set forth in  claim 1 , wherein during fuel cut control which stops fuel injection from the fuel injector, even when the condition for executing early exhaust valve closing control stands, the execution of said early exhaust valve closing control is prohibited regardless of the output torque and engine speed when the wall fuel deposition amount stuck to the intake port wall is smaller then a limit fuel amount. 
     
     
       3. A control device as set forth in  claim 2 , wherein said wall fuel deposition amount is estimated based on the combustion state of the preceding cycle, valve timings of the intake valve and exhaust valve, pressure inside the intake passage, amount of air passing through the intake port in the current cycle, and fuel injection amount of the current cycle. 
     
     
       4. A control device as set forth in  claim 2 , wherein, right after the end of fuel cut control, even if said condition for executing early exhaust valve closing control does not stand, said early exhaust valve closing control is executed. 
     
     
       5. A control device as set forth in  claim 4 , wherein when executing early exhaust valve closing control right after the end of fuel cut control, the amount of advance of the exhaust value in said early exhaust valve closing control is set in accordance with the wall fuel deposition amount at the time of end of said fuel cut control. 
     
     
       6. A control device as set forth in  claim 1 , wherein, during fuel cut control which stops fuel injection from the fuel injector, the amount of advance of the closing timing of the exhaust valve in said early exhaust valve closing control is controlled in accordance with the wall fuel deposition amount which is stuck to the intake port wall. 
     
     
       7. A control device of an internal combustion engine provided with a fuel injector which injects fuel to the inside of an intake port and an exhaust variable valve timing mechanism able to change a valve timing of an exhaust valve, when conditions for executing early exhaust valve closing control stand, the control device executing early exhaust valve closing control which advances a closing timing of the exhaust valve so as to make combustion gas in a combustion chamber flow back into an intake port when an intake valve opens,
 wherein the control device is further provided with a torque detecting means for detecting an output torque which is output by an engine body and, 
 wherein at the time of a deceleration operation of the internal combustion engine, even when the condition for executing early exhaust valve closing control stands, an ignition timing is advanced when it is predicted that the output torque which is detected by said torque detecting means will become smaller than a limit torque. 
 
     
     
       8. A control device of an internal combustion engine provided with a fuel injector which injects fuel to the inside of an intake port and an exhaust variable valve timing mechanism able to change a valve timing of an exhaust valve, when conditions for executing early exhaust valve closing control stand, the control device executing early exhaust valve closing control which advances a closing timing of the exhaust valve so as to make combustion gas in a combustion chamber flow back into an intake port when an intake valve opens,
 wherein at the time of a deceleration operation of the internal combustion engine, even when the condition for executing early exhaust valve closing control stands, execution of the early exhaust valve closing control is prohibited when it is predicted that an engine speed will become lower than a limit speed. 
 
     
     
       9. A control device of an internal combustion engine provided with a fuel injector which injects fuel to the inside of an intake port and an exhaust variable valve timing mechanism able to change a valve timing of an exhaust valve, when conditions for executing early exhaust valve closing control stand, the control device executing early exhaust valve closing control which advances a closing timing of the exhaust valve so as to make combustion gas in a combustion chamber flow back into an intake port when an intake valve opens,
 wherein at the time of a deceleration operation of the internal combustion engine, even when the condition for executing early exhaust valve closing control stands, an ignition timing is advanced when it is predicted that the engine speed will become smaller than a limit speed.